Field of the Invention
The present invention concerns wireless communications, and more specifically, methods and apparatuses of indicating the type of a frame.
Related Art
Machine-to-machine (M2M) systems draw attention as next-generation communication technology and are being standardized in order to be supported by IEEE 802.11 WLAN. M2M system means a network in which a machine, not a human being, serves to perform communication to send and receive information. A temperature sensor, moisture sensor, camera, home appliance, such as a TV, and a bulky machine such as a factory machine or vehicle, may be an M2M element. Recently, as various communication services such as smart grid, e-Health, and ubiquitous, appear, M2M techniques are put to use to support such services. M2M system has the following characteristics.
1) Many stations: M2M assumes a great number of stations unlike existing networks because sensors installed in the home or business, as well as machines owned by individuals need to be also taken into account. Accordingly, a significant number of stations may be linked to a single AP.
2) Low traffic load per station: Since an M2M terminal has a traffic pattern in which it collects ambient information and reports it, it need not often send information and it send a relatively small amount of information.
3) Uplink-centered: M2M has a structure in which it receives a command on downlink, takes action, and then reports a result on uplink. Main data is normally sent on uplink, and thus, M2M is uplink-centered.
4) Long-lifespan station: An M2M terminal is primarily battery-powered, and a user has difficulty in often recharging. Accordingly, it is required to guarantee long lifespan by minimizing battery consumption.
5) Automatic restoration function: An M2M terminal is difficult for a human being to directly manipulate under a specific situation, and thus, it requires a self-restoration function.